I am for this argument because if you believe in a religion you think its real so people who think Santa is real shouldn't be told otherwise. A fact doesn't make a reality, its your perceptions that makes your reality.
St. Nicholas just like Jesus, Buddha, or Muhammad were actual historical figures. We have testimony of where St. nicholas lived, worked, and how he came to be known as such a great man. This information is well known facts. If you're trying to make a point of whether the supernatural claims are true or not you have to look deeper into eyewitness report of whether they are true or beyond reasonable doubt. For example, while St. Nicholas was alive in the 3rd century no one ever claimed that he lived in the North Pole and delivered presents to kids on magic reindeer. That idea came about in the 1820's. While some religious figures had eyewitness's see them perform supernatural things.
You can't say fact isn't real then make a "factual claim"